Allow `CURRENT_TIMESTAMP` string to be overridden by settings django_pg_current_timestamp._current_timestamp_sql to a different value (e.g. `clock_timestamp`).
Allow `CURRENT_TIMESTAMP` string to be overridden by settings django_pg_current_timestamp._current_timestamp_sql to a different value (e.g. `clock_timestamp`).

jaytaylor/django-pg-current-timestamp,threatstream/django-pg-current-timestamp